Liquid ejection device

ABSTRACT

An ink ejection device comprises: an ink supply section including a plurality of ink chambers respectively containing the plural kinds of inks; and a head section having plural groups of nozzles and ejecting the plural kinds of inks to be supplied from the ink supply section. The head section includes a plurality of supply ports which are aligned in the scanning direction and through which the plural kinds of inks are supplied. The ink supply section includes: a plurality of connection passages respectively connecting the plurality of supply ports to the ink chambers containing the inks to be supplied respectively to the supply ports; and a plurality of air discharge passages connected respectively to the plurality of ink chambers. Then, the plurality of ink chambers are aligned in the conveying direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2013-201418 filed in Japan on Sep. 27, 2013and Patent Application No. 2014-189706 filed in Japan on Sep. 18, 2014,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a liquid ejection device.

BACKGROUND

Japanese Patent No. 4985639 discloses an ink jet printer as an exampleof a liquid ejection device. The printer includes: an ink jet head (aliquid ejection section) ejecting ink; and a buffer tank (a liquidsupply section) arranged above the ink jet head and supplying the ink tothe ink jet head. The ink jet head and the buffer tank are mounted on acarriage moving in the scanning direction and hence move in the scanningdirection together with the carriage.

The ink jet head includes four ink introduction ports (supply ports)through which inks of four colors (black, magenta, yellow, and cyan) aresupplied respectively. Here, one ink introduction port is provided forblack ink and one ink introduction port is provided for magenta ink.However, two ink introduction ports are provided for yellow ink and twoink introduction ports are provided for cyan ink. That is, the ink jethead includes a total of six ink introduction ports. Then, the six inkintroduction ports are aligned in the scanning direction of the ink jethead.

The buffer tank is connected to four ink tanks through tubes. Then, theinks of four colors are supplied from the four ink tanks to the buffertank. The buffer tank includes six air-liquid separation chambersrespectively corresponding to the six ink introduction ports of the inkjet head. Here, two air-liquid separation chambers are provided foryellow ink and two air-liquid separation chambers are provided for cyanink similarly to the ink introduction ports. Then, each two air-liquidseparation chambers into which ink of the same color is introduced arein communication with each other. Further, the six air-liquid separationchambers are aligned in the scanning direction of the ink jet head incorrespondence to the six ink introduction ports. The ink supplied fromeach ink tank to the buffer tank flows into the air-liquid separationchamber. Here, in a case that air is mixed in the supplied ink, when theink flows from the air-liquid separation chamber toward the inkintroduction port of the ink jet head located thereunder, the air mixedin the ink is separated from the ink and then collected in the upperportion of the air-liquid separation chamber. Thus, the ink in thebuffer tank is supplied to the ink jet head after the air is separatedand removed in the air-liquid separation chamber.

SUMMARY

In Japanese Patent No. 4985639, the buffer tank arranged above the inkjet head includes the six air-liquid separation chambers aligned in thescanning direction in correspondence to the six ink introduction portsof the ink jet head. Here, as the ink is consumed by the ink jet head,the air (air bubbles) separated from the ink increases in the upperportion of the air-liquid separation chamber. Thus, in a case that thearea of the air-liquid separation chamber is small, the air-liquidseparation chamber is rapidly filled with the air. Accordingly, the areaof the air-liquid separation chamber is preferred to be as large aspractical. Nevertheless, in the configuration like that in JapanesePatent No. 4985639, when the area of each air-liquid separation chamberis increased, the length of the buffer tank in the scanning direction isalso increased. Then, when the length of the buffer tank in the scanningdirection is increased, this causes an increase in the necessaryscanning range of the carriage on which the ink jet head and the buffertank are mounted and hence directly causes a size increase in theprinter body.

An object of the present disclosure is to achieve an increase in thearea of the liquid chamber separating gas from liquid without thenecessity of size increase of the liquid supply section in the scanningdirection.

The liquid ejection device according to a first aspect is characterizedby a liquid ejection device comprising: a liquid supply sectionincluding a plurality of liquid chambers respectively configured tocontain plural kinds of liquids; and a liquid ejection section includingplural nozzle groups of one or plural nozzle(s) and configured to ejectthe plural kinds of liquids to be supplied from the liquid supplysection, wherein the liquid ejection section includes a plurality ofsupply ports which are aligned in a first direction and through whichthe plural kinds of liquids are supplied, wherein the liquid supplysection includes: a plurality of connection passages respectivelyconnecting the plurality of supply ports of the liquid ejection sectionto the liquid chambers configured to contain the liquids to be suppliedrespectively to the supply ports; and a plurality of air dischargepassages connected respectively to the plurality of liquid chambers, andwherein the plurality of liquid chambers are aligned in a seconddirection intersecting with the first direction.

According to the first aspect, plural kinds of liquids introduced intothe liquid supply section flow into the liquid chambers corresponding tothe kinds of the liquids. Each liquid having flowed into the liquidchamber is supplied through the connection passage to the supply port ofthe liquid ejection section. When the liquid flows from the liquidchamber, gas mixed in the liquid is separated and left from the liquidand then collected in the upper portion of the liquid chamber. The gasis discharged through the air discharge passage connected to the liquidchamber.

Further, the plurality of supply ports of the liquid ejection sectionare aligned in the first direction. On the other hand, the plurality ofliquid chambers connected to the plurality of supply ports are alignedin the second direction intersecting with the first direction. Thus, ina state that the size of the liquid supply section in the firstdirection is controlled small, the length of each liquid chamber in thefirst direction is allowed to be increased so that a larger area of eachliquid chamber is allowed to be ensured.

According to the first aspect, the plurality of supply ports of theliquid ejection section are aligned in the first direction. In contrastto this configuration, the plurality of liquid chambers connected to theplurality of supply ports are aligned in the second directionintersecting with the first direction. Thus, in a state that the size ofthe liquid supply section in the first direction is controlled small, alarger area of each liquid chamber is allowed to be ensured.

The above and further objects and features will more fully be apparentfrom the following detailed description with accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic plan view of a printer according to the presentembodiment.

FIG. 2 is a top view of an ink ejection device.

FIG. 3 is a sectional view taken along line III-III in FIG. 2.

FIG. 4 is a top view of a head section.

FIG. 5A is an enlarged view of part A in FIG. 4.

FIG. 5B is a sectional view taken along line B-B in FIG. 5A.

FIG. 6 is a horizontal sectional view of a distribution member.

FIG. 7 is a top view of an ink ejection device constructed such that inkchambers in the same number as supply ports are aligned in the scanningdirection.

FIG. 8 is a top view of a head section according to Modification 1.

FIGS. 9A to 9D are horizontal sectional views of a distribution memberaccording to Modification 1.

FIG. 10 is a top view of a head section according to Modification 2.

FIG. 11 is horizontal sectional views of a distribution member accordingto Modification 2.

FIG. 12 is an enlarged sectional view showing a position of a manifoldof the head section according to Modification 2.

FIG. 13 is a top view of an ink ejection device according to amodification.

FIG. 14 is a top view of an ink ejection device according to anothermodification.

FIG. 15 is a top view of a head section according to anothermodification.

DETAILED DESCRIPTION

The present embodiment is described below. FIG. 1 is a schematic planview of a printer according to the present embodiment.

(Outline Configuration of Printer)

As illustrated in FIG. 1, a printer 1 comprises a platen 2, a carriage3, an ink ejection device 4, a holder 5, a paper feed roller 6, a paperdischarge roller 7, a cap device 8, a switching device 9, a suction pump10, a waste liquid tank 11, and a control device 12. In the followingdescription, the near side with respect to the paper of FIG. 1 isreferred to as the “upward” of the printer 1 and the far side withrespect to the paper is referred to as the “downward” of the printer 1.Further, the forward and the backward as well as the rightward and theleftward illustrated in FIG. 1 are respectively referred to as the“forward and backward directions” and the “right and left directions” ofthe printer 1. The following description is given by using thesedefinitions of directions: forward, backward, rightward, leftward,upward, and downward, and the like.

A recording paper sheet 100 serving as a recording medium is placed onthe upper surface of the platen 2. Further, above the platen 2, twoguide rails 15 and 16 are provided that extend in to parallel to theright and left directions (also referred to as scanning direction) inFIG. 1.

The carriage 3 is attached to the two guide rails 15 and 16 and movablealong the two guide rails 15 and 16 in the scanning direction in aregion opposing the platen 2. Further, a drive belt 17 is attached tothe carriage 3. The drive belt 17 is an endless-shaped belt wound aroundtwo pulleys 18 and 19. The pulley 18 is linked to a carriage drive motor14. When the pulley 18 is rotated by the carriage drive motor 14, thedrive belt 17 runs so that the carriage 3 performs reciprocatingmovement in the scanning direction.

The ink ejection device 4 (an example of the liquid ejection device) ismounted on the carriage 3. The ink ejection device 4 includes a headsection 20 (an example of the liquid ejection section) and an ink supplysection 21 (an example of the liquid supply section). Further, four inkcartridges 30 respectively storing inks of four colors (black, yellow,cyan, and magenta) are mounted on the holder 5 in an attachable anddetachable manner. In the following description, components of theprinter 1 corresponding to the inks of black (K), yellow (Y), cyan (C),and magenta (M) are designated respectively by reference numeralsobtained by suitably appending “k” indicating black, “y” indicatingyellow, “c” indicating cyan, and “m” indicating magenta to the referencenumerals indicating these components so as to express the correspondenceto which inks. For to example, an ink cartridge 30 k indicates an inkcartridge 30 storing black ink. Further, inks of three colors consistingof yellow, cyan, and magenta other than the black ink are genericallyreferred to as “color inks”, in some cases.

The head section 20 includes a plurality of nozzles 47 formed in thelower surface (see FIG. 4). Then, inks are ejected through the nozzles47. Details of the passage structure and the like of the head section 20are described later.

The ink supply section 21 is arranged above the head section 20 andsupplies the inks of four colors to the head section 20. The ink supplysection 21 includes a sub tank 31. Then, the sub tank 31 is connectedthrough a tube joint 23 to four tubes 22 that are connected to theholder 5. Here, in place of the intervention of the tube joint 23, thefour tubes 22 may be connected to the sub tank 31 one by one. Further,an air discharge section 24 is provided in the sub tank 31. The airdischarge section 24 is employed for discharging air in the sub tank 31before the air moves to the head section 20. Ink passages for fourcolors formed in the sub tank 31 are connected respectively to four airdischarge ports 24 a of the air discharge section 24. Here, in each airdischarge port 24 a, a valve (not illustrated) is provided that switchescommunication and close relative to the outside.

The paper feed roller 6 and the paper discharge roller 7 are driven androtated by a motor (not illustrated) in synchronization with each other.The paper feed roller 6 and the paper discharge roller 7 convey therecording paper sheet 100 placed on the platen 2 toward the conveyingdirection (forward) illustrated in FIG. 1, in cooperation with eachother.

In the printer 1, in a state that the paper feed roller 6 and the paperdischarge roller 7 convey the recording paper sheet 100 in the conveyingdirection and in a state that the ink ejection device 4 is moved in thescanning direction together with the carriage 3, the inks are ejectedthrough the plurality of nozzles 47 of the head section 20 so that adesired image or the like is printed on the recording paper sheet 100.

The cap device 8 is arranged at a position on one side (the right-handside) of the platen 2 in the scanning direction. The cap device 8includes a nozzle cap 25 and an air discharge cap 26. Further, the capdevice 8 is driven by a cap raising and lowering mechanism (notillustrated) and is allowed to be raised and lowered in the up and downdirections (directions perpendicular to the paper of FIG. 1).

When the carriage 3 moves to the right-hand side of the platen 2, thenozzle cap 25 opposes the lower surface of the head section 20 and theair discharge cap 26 opposes the four air discharge ports 24 a of theair discharge section 24. In this state, when the cap device 8 israised, the cap device 8 is attached to the ink ejection device 4. Atthat time, the nozzle cap 25 covers the plurality of nozzles 47 of thehead section 20 and the air discharge cap 26 is connected to the fourair discharge ports 24 a of the air discharge section 24. The airdischarge cap 26 is provided with four bar-shaped opening and closingmembers 27 respectively opening and closing the valves in the four airdischarge ports 24 a. Although detailed description is omitted, in astate that the air discharge cap 26 is connected to the four airdischarge ports 24 a, the four bar-shaped opening and closing members 27are driven up and down by a drive mechanism (not illustrated) andthereby inserted into the air discharge ports 24 a from below so as todrive the valves provided in the air discharge ports 24 a.

The nozzle cap 25 and the air discharge cap 26 are connected through theswitching device 9 to the suction pump 10. The switching device 9switches the destination of communication of the suction pump 10 to thenozzle cap 25 or the air discharge cap 26 and thereby allows selectiveexecution of suction purge and air discharging purge described below.

(Suction purge) In a state that the nozzle cap 25 covers the pluralityof nozzles 47 of the head section 20, the pressure in the nozzle cap 25is reduced by the suction pump 10. Then, inks are suctioned anddischarged respectively through the plurality of nozzles 47. Thisrealizes discharging of foreign substances, air bubbles, or inks whoseviscosity has been increased by drying and the like, in the head section20.

(Air discharging purge) In a state that the air discharge cap 26 isconnected to the air discharge ports 24 a and that the valves in the airdischarge ports 24 a are opened by the opening and closing members 27, anegative pressure is applied on the air discharge ports 24 a by thesuction pump 10. By virtue of this, air in the ink supply section 21 isdischarged through the air discharge ports 24 a before the air move tothe head section 20.

Here, at the time of suction purge or air discharging purge, the inksdischarged from the head section 20 or the ink supply section 21 of theink ejection device 4 are sent to the waste liquid tank 11 connected tothe suction pump 10.

The control device 12 controls the above-mentioned various parts of theprinter 1 so as to execute various kinds of processing such as printingon the recording paper sheet 100. For example, on the basis of a printinstruction transmitted from an external device such as a personalcomputer, the control device 12 controls the ink ejection device 4, thecarriage drive motor 14, and the like and thereby prints an image or thelike on the recording paper sheet 100. Further, the control device 12controls the switching device 9, the suction pump 10, and the like andthereby executes suction purge or air discharging purge described above.

(Details of Ink Ejection Device)

Next, details of the configuration of the ink ejection device 4 aredescribed below. FIG. 2 is a top view of the ink ejection device 4. FIG.3 is a sectional view taken along line III-III in FIG. 2. As describedabove, the ink ejection device 4 includes the head section 20 and theink supply section 21 arranged above the head section 20. For simplicityof the diagram, in FIG. 3, the sub tank 31 alone of the ink supplysection 21 is illustrated in sectional view while the head section 20and a distribution member 32 of the ink supply section 21 areillustrated in side view.

(Configuration of Head Section)

First, the configuration of the head section 20 is described below. FIG.4 is a top view of the head section 20. FIG. 5A is an enlarged view ofpart A in FIG. 4. FIG. 5B is a sectional view taken along line B-B inFIG. 5A. As illustrated in FIGS. 4, 5A, and 5B, the head section 20includes a passage unit 40 and a piezoelectric actuator 41.

(Passage Unit)

As illustrated in FIG. 5B, the passage unit 40 is constructed bystacking five plates 42 to 46. The lowermost plate 46 among the fiveplates 42 to 46 is a nozzle plate in which the plurality of nozzles 47are formed. On the other hand, in the remaining four plates 42 to 45 onthe upper side, passages such as manifolds 50 and pressure chambers 51in communication with the plurality of nozzles 47 are formed.

With reference mainly to FIG. 4, the arrangement of the plurality ofnozzles 47 formed in the nozzle plate 46 is described below. In thenozzle plate 46, the plurality of nozzles 47 are arranged with a pitch Palong the conveying direction (an example of the second direction). Theplurality of nozzles 47 constitute a total of eight nozzle groups 48aligned in the scanning direction (an example of the first direction).Here, in the present embodiment, the direction (the second direction) ofarrangement of the plurality of nozzles 47 is perpendicular to thescanning direction (the first direction). However, this configuration isnot indispensable. That is, the direction of arrangement of the nozzles47 may intersect with the scanning direction at an angle other than 90degrees.

The eight nozzle groups 48 consist of two nozzle groups 48 k 1 and 48 k2 ejecting black ink, two nozzle groups 48 y 1 and 48 y 2 ejectingyellow ink, two nozzle groups 48 c 1 and 48 c 2 ejecting cyan ink, andtwo nozzle groups 48 m 1 and 48 m 2 ejecting magenta ink. Here, in eachtwo nozzle groups 48 (e.g., the two nozzle groups 48 k 1 and 48 k 2)ejecting an ink of the same color, the positions of the nozzles 47 ofone group are shifted from those of the other group in the direction ofarrangement of the nozzles by half the pitch P (by P/2) in each nozzlegroup 48.

The two nozzle groups 48 k 1 and 48 k 2 of black ink are arrangedadjacent to each other in the center portion in the scanning direction.Then, the two nozzle groups 48 y 1 and 48 y 2 of yellow ink are arrangedrespectively on both sides of the two nozzle groups 48 k 1 and 48 k 2 ofblack ink in the scanning direction in a manner that the two nozzlegroups 48 k 1 and 48 k 2 are located in between. Further, the two nozzlegroups 48 k 1 and 48 c 2 of cyan ink are arranged on both sides of thesefour nozzle groups 48 k 1, 48 k 2, 48 y 1, and 48 y 2 and the two nozzlegroups 48 m 1 and 48 m 2 of magenta ink are arranged on both sides ofthese six nozzle groups 48 k 1, 48 k 2, 48 y 1, 48 y 2, 48 c 1, and 48 c2. That is, the nozzle groups 48 of the inks of four colors consistingof black, yellow, cyan, and magenta are arranged in left-right symmetry.

According to this configuration, in so-called bidirectional printing,when each four nozzle groups 48 provided on the left or right side areused selectively depending on the situation whether the carriage 3 movesin one of the scanning direction or in the other one of the scanningdirection, each dot is formed by ejecting the inks of four colors ontothe recording paper sheet 100 always in the same order (in the order ofmagenta, cyan, yellow, and black) regardless of the direction of movingof the carriage 3. That is, when the nozzles are arranged in theabove-mentioned manner, the color texture of each dot is maintainedhomogeneous so that high-quality recording of an image or the like isachievable even in a case that bidirectional printing is employed thatenhances the recording rate.

Here, the arrangement of the nozzle groups 48 m, 48 c, and 48 y of thecolor inks of three colors arranged separately onto each of the rightand left sides of the nozzle groups 48 k of black ink is not limited toa left-right symmetric arrangement like that of FIG. 4 and may bechanged suitably. For example, on both of the right and left sides ofthe nozzle groups 48 k of black ink, the nozzle groups 48 m, 48 c, and48 y of the color inks of three colors may be arranged in the same orderof magenta→cyan→yellow from left to right.

Next, the structure of the passages formed in the four plates 42 to 45on the upper side of the passage unit 40 and formed in communicationwith the plurality of nozzles 47 is described below. First, asillustrated in FIG. 4, seven supply ports 49 aligned in the scanningdirection are formed in the upper surface of the end part of the passageunit 40 in the upstream of the conveying direction. The supply ports 49receives the inks of four colors supplied from the ink supply section 21described later. The seven supply ports 49 consist of a supply port 49 kof black ink, two supply ports 49 y 1 and 49 y 2 of yellow ink, twosupply ports 49 c 1 and 49 c 2 of cyan ink, and two supply ports 49 m 1and 49 m 2 of magenta ink. Here, FIG. 4 illustrates a mode that theseven supply ports 49 of the head section 20 are aligned in line on aplane. However, employable configurations are not limited to thisarrangement. For example, the positions of the seven supply ports 49 maybe somewhat different from each other in the up and down directions.Further, the seven supply ports 49 may be aligned along a directionslightly inclined from a horizontal direction (the scanning direction,the first direction).

The seven supply ports 49 are aligned in the scanning direction in theorder corresponding to the above-mentioned arrangement of the nozzlegroups 48 of the inks of four colors. More specifically, first, thesupply port 49 k of black ink is arranged in the center portion in thescanning direction. Then, the supply port 49 y of yellow ink, the supplyport 49 c of cyan ink, and the supply port 49 m of magenta ink arearranged in left-right symmetry in the order of the supply port 49 y ofyellow ink, the supply port 49 c of cyan ink, and the supply port 49 mof magenta ink starting at the vicinity of the supply port 49 k of blackink toward each of the outer sides (both left and right sides) in thescanning direction. That is, the two supply ports 49 y of yellow ink arearranged in a manner that the supply port 49 k of black ink is locatedin between in the scanning direction. Then, the two supply ports 49 c ofcyan ink are arranged in a manner that the three supply ports 49 k and49 y are located in between in the scanning direction. Further, the twosupply ports 49 m of magenta ink are arranged in a manner that the fivesupply ports 49 k, 49 y, and 49 c are located in between in the scanningdirection. Here, the supply port 49 k of black ink has a larger holesize than the other six supply ports 49 because the black ink need besupplied to both of the two nozzle groups 48 k 1 and 48 k 2.

Further, in the passage unit 40, seven manifolds 50 (an example of thecommon passage) are formed that extend respectively in the conveyingdirection. The backward end parts of the seven manifolds 50 areconnected respectively to the seven supply ports 49. The manifold 50 kreceives black ink supplied through the supply port 49 k. Further, themanifolds 50 y 1 and 50 y 2 receive yellow ink supplied through thesupply ports 49 y 1 and 49 y 2. The manifolds 50 c 1 and 50 c 2 receivecyan ink supplied through the supply ports 49 c 1 and 49 c 2. Themanifolds 50 m 1 and 50 m 2 receive magenta ink supplied through thesupply ports 49 m 1 and 49 m 2. Here, as for the passage of black ink,similarly to the passages of the other inks, two supply ports 49 k maybe provided respectively in correspondence to the two nozzle groups 48 k1 and 48 k 2 and, similarly, two manifolds 50 k may be provided.

The manifolds 50 of the inks of four colors consisting of black, yellow,cyan, and magenta are arranged in left-right symmetry similarly to theabove-mentioned nozzle groups 48 of the inks of four colors. That is,the manifold 50 k of black ink is arranged in the center portion in thescanning direction. Then, the two manifolds 50 y 1 and 50 y 2 of yellowink are arranged respectively on both sides of the manifold 50 k in amanner that the manifold 50 k is located in between. The two manifolds50 c 1 and 50 c 2 of cyan ink are arranged respectively on both sides ofthe manifolds 50 k and 50 y and the two manifolds 50 m 1 and 50 m 2 ofmagenta ink are arranged respectively on both sides of the manifolds 50k, 50 y, and 50 c.

Further, the passage unit 40 includes the plurality of pressure chambers51 respectively corresponding to the plurality of nozzles 47. Theplurality of pressure chambers 51 are formed in the plate 42 located asthe uppermost layer of the passage unit 40 and arranged respectively incorrespondence to the plurality of nozzles 47. As illustrated in FIG. 4,the pressure chambers 51 are arranged at positions above the manifolds50 in eight rows along the conveying direction respectively incorrespondence to the eight nozzle groups 48. Here, the two nozzlegroups 48 k 1 and 48 k 2 of black ink are arranged adjacent to eachother in the scanning direction. Further, the pressure chamber rows oftwo rows corresponding to the two nozzle groups 48 k 1 and 48 k 2 arealso adjacent to each other. Thus, both of the two pressure chamber rowsof black ink are in communication with one manifold 50 k locatedimmediately thereunder. On the other hand, as for the pressure chamberrows corresponding to the other nozzle groups 48, each pressure chamberrow is in communication with one manifold 50 located immediatelythereunder. According to this configuration, as indicated by an arrow inFIG. 5B, in the passage unit 40, a plurality of individual passages areformed each of which branches from each manifold 50 and then goesthrough the pressure chamber 51 to the nozzle 47.

(Piezoelectric Actuator)

The piezoelectric actuator 41 is joined to the upper surface of thepassage unit 40 such as to cover the plurality of pressure chambers 51.As illustrated in FIGS. 4, 5A, and 5B, the piezoelectric actuator 41includes an ink sealing film 52, two piezoelectric layers 53 and 54, aplurality of individual electrodes 55, and a common electrode 56.

The ink sealing film 52 is composed of a thin film fabricated from amaterial having low ink permeability, for example, a metallic materialsuch as stainless steel. The ink sealing film 52 is joined to the uppersurface of the passage unit 40 such as to cover the plurality ofpressure chambers 51.

The two piezoelectric layers 53 and 54 are respectively fabricated froma piezoelectric material containing, as a main component, lead zirconatetitanate which is mixed crystal of lead titanate and lead zirconate. Thepiezoelectric layers 53 and 54 are arranged on the upper surface of theink sealing film 52 with the piezoelectric layers 53 and 54 beingstacked with each other.

The plurality of individual electrodes 55 are arranged on the uppersurface of the upper piezoelectric layer 53. More specifically, asillustrated in FIGS. 4, 5A, and 5B, each of the individual electrodes 55is arranged in a region of the upper surface of the piezoelectric layer53 that opposes the center portion of the pressure chamber 51. Theplurality of individual electrodes 55 are arranged in correspondence tothe plurality of pressure chambers 51 and hence constitute a total ofeight individual electrode rows. An individual terminal 57 extends fromeach of the individual electrodes 55. The plurality of individualterminals 57 are connected to a wiring member (not illustrated) on whicha driver IC 58 is mounted. According to this configuration, theplurality of individual electrodes 55 are electrically connected to thedriver IC 58. Each of the individual electrodes 55 receives apredetermined drive potential or a ground potential selectively appliedby the driver IC 58.

The common electrode 56 is arranged between the two piezoelectric layers53 and 54. The common electrode 56 opposes the plurality of individualelectrodes 55 with the piezoelectric layer 53 in between. Althoughillustration of a detailed electric connection structure is omitted, aconnection terminal extends also from the common electrode 56 to theupper surface of the piezoelectric layer 53. Then, similarly to theplurality of individual electrodes 55, the connection terminal isconnected to a wiring member (not illustrated). The common electrode 56is connected to a ground wiring formed in the wiring member so that thepotential of the common electrode 56 is maintained always at the groundpotential.

Here, a part of the piezoelectric layer 53 (referred to as an activepart 53 a) located between the individual electrode 55 and the commonelectrode 56 is polarized in the thickness direction (downward). Theactive part 53 a is a part where a potential difference is generatedbetween the individual electrode 55 and the common electrode 56 so thatan electric field generates in the thickness direction and causes apiezoelectric deformation (piezoelectric strain).

The operation of the piezoelectric actuator 41 is described below. Whenthe driver IC 58 applies a drive potential onto a given individualelectrode 55, a potential difference arises between this individualelectrode 55 and the common electrode 56. At that time, an electricfield generates on the active part 53 a of the piezoelectric layer 53 inthe thickness direction (downward). The direction of the electric fieldagrees with the direction of polarization of the active part 53 a. Thus,the active part 53 a is contracted in the plane direction. Then, inassociation with the contraction of the active part 53 a, a deformationso as to be convex toward the pressure chamber 51 is generated in thetwo piezoelectric layers 53 and 54. This causes a change in the volumeof the pressure chamber 51 and hence generates a pressure wave in theindividual passage including the pressure chamber 51. By virtue of this,ejection energy is imparted to the ink so that a droplet of the ink isejected through the nozzle 47.

(Configuration of Ink Supply Section)

Next, the ink supply section 21 is described below. As illustrated inFIGS. 2 and 3, the ink supply section 21 includes the sub tank 31 andthe distribution member 32.

The sub tank 31 is a member formed from synthetic resin or the like andhaving a rectangular shape in plan view. The sub tank 31 includes fourink chambers 61 (an example of the liquid chambers) respectivelycontaining the inks of four colors. As illustrated in FIG. 2, each inkchamber 61 has, in plan view, a rectangular shape elongated in thescanning direction. The four ink chambers 61 are aligned in the order ofblack, yellow, cyan, and magenta along the conveying direction. Here,the lengths of the four ink chambers 61 in the scanning direction areshorter in the order of arrangement of the ink chambers 61 toward thedownstream (the forward side) of the conveying direction. Further, thefour ink chambers 61 have mutually the same length in the conveyingdirection. Thus, the areas of the four ink chambers 61 are smaller inthe order of arrangement of the ink chambers 61 toward the downstream ofthe conveying direction. Further, the four ink chambers 61 arerespectively located on right side of the sub tank 31 in alignment witheach other and hence the positions of the right ends thereof in thescanning direction are aligned with each other. Here, FIG. 2 illustratesa mode that the four ink chambers 61 are aligned in line on a plane.However, employable configurations are not limited to this arrangement.That is, the positions of the four ink chambers 61 may be somewhatdifferent in the up and down directions. Further, the four ink chambers61 may be aligned along a direction slightly inclined from a horizontaldirection (the conveying direction, the second direction).

In a portion of the sub tank 31 on the forward side relative to the fourink chambers 61, four ink introduction passages 64 (an example of theliquid introduction sections) are formed that respectively extend in theconveying direction and are connected respectively to the four inkchambers 61. Further, the tube joint 23 is attached to the upper surfaceof the left half part of the forward end part of the sub tank 31. Thefour ink introduction passages 64 are respectively connected through thetube joint 23 and the four tubes 22 to the four ink cartridges 30 (anexample of the liquid storage sections; see FIG. 1) mounted on theholder 5. Further, as described above, since the four ink chambers 61are located on the right side of the sub tank 31 in alignment with eachother, a vacant region is present on the left side of the ink chambers61 located on the more forward side and having the shorter lengths inthe scanning direction. In this region, ink introduction passages 64 arearranged for introducing the inks to the ink chambers 61 arranged on themore backward side. That is, the ink chambers 61 located on the moreforward side (e.g., the ink chamber 61 m) and the ink introductionpassages 64 (the ink introduction passages 64 k, 64 y, and 64 c)connected to the ink chambers 61 located on the backward side relativeto the ink chambers 61 located on the more forward side (the ink chamber61 m) are aligned in the scanning direction.

In the lower wall of the sub tank 31, four ejection holes 62 are formedthat are respectively in communication with the four ink chambers 61.The four ejection holes 62 are aligned in the forward and backwarddirections in the center portion of the scanning direction of the subtank 31 in accordance with the order of arrangement of the four inkchambers 61. The inks of four colors contained in the four ink chambers61 are sent through the four ejection holes 62 to the distributionmember 32 arranged under the ejection holes 62 and described later.

In the right end part of the sub tank 31, four air discharge passages 65are formed that are connected respectively to the four ink chambers 61.Further, the air discharge section 24 is provided in the rightside-surface of the sub tank 31. The four air discharge passages 65 areconnected respectively to the four air discharge ports 24 a of the airdischarge section 24.

Here, as illustrated in FIG. 3, the ink chambers 61, the inkintroduction passages 64, and the air discharge passages 65 describedabove are concave passages opened upward. Then, in a manner of coveringthe concave passages together from above, a flexible damper film 34composed of a synthetic resin film or the like is provided almost overthe entirety of the upper surface of the sub tank 31. Each ink chamber61 is covered by the damper film 34 from above, and thereby each inkchamber 61 serves also as a damper chamber attenuating a pressurefluctuation in the ink.

As illustrated in FIGS. 2 and 3, the distribution member 32 is a memberhaving a rectangular shape in plan view and arranged between the headsection 20 and the sub tank 31. The distribution member 32 is connectedthrough communicating members 35 to the ejection holes 62 of the subtank 31. Further, the distribution member 32 is connected also to thesupply ports 49 of the head section 20 through communicating members 36.FIG. 6 is a horizontal sectional view of the distribution member 32.

As illustrated in FIGS. 3 and 6, in the backward end part of thedistribution member 32, seven ink discharge ports 66 are formed that arearranged respectively at positions immediately above the seven supplyports 49 of the head section 20 and aligned in the scanning direction.The seven ink discharge ports 66 are respectively connected through thecommunicating members 36 to the seven ink supply ports 49 of the headsection 20.

Further, the distribution member 32 includes four connection passages 67supplying the inks of four colors sent from the four ink chambers 61 ofthe sub tank 31 through the ejection holes 62, respectively to the sevensupply ports 49 of the head section 20. Each of the four connectionpassages 67 includes a communicating hole 68 in communication with theejection hole 62 of the sub tank 31 and a supply passage(s) 69connecting the communicating hole 68 to the ink discharge port(s) 66.The four communicating holes 68 are aligned in the forward and backwarddirections in correspondence to the arrangement of the four ejectionholes 62 of the sub tank 31 in the center portion of the scanningdirection of the distribution member 32.

Among the four communicating holes 68, the communicating hole 68 k ofblack ink is located on the most backward side. Then, one supply passage69 k extends backward from the communicating hole 68 k. The one supplypassage 69 k is connected to the ink discharge port 66 k of black ink.Here, the connection passage 67 k of black ink is an example of thefirst connection passage and the supply port 49 k of black ink is anexample of the first supply port. Further, the ink chamber 61 k of blackink is an example of the first liquid chamber.

On the other hand, two supply passages 69 extend in the right and leftdirections from each of the communicating hole 68 y of yellow ink, thecommunicating hole 68 c of cyan ink, and the communicating hole 68 m ofmagenta ink. Further, each of the supply passages 69 is bent in themiddle so as to extend backward and then is connected to the inkdischarge port 66. That is, the two supply passages 69 y 1 and 69 y 2 ofyellow ink are connected respectively to the two ink discharge ports 66y 1 and 66 y 2 of yellow ink. Similarly, the two supply passages 69 c 1and 69 c 2 of cyan ink are connected respectively to the two inkdischarge ports 66 c 1 and 66 c 2 of cyan ink, and the two supplypassages 69 m 1 and 69 m 2 of magenta ink are connected respectively tothe two air discharge ports 66 m 1 and 66 m 2 of magenta ink. Here, eachof the connection passages 67 y, 67 c, and 67 m of the color inks ofthree colors is an example of the second connection passage. Thecommunicating holes 68 y, 68 c, and 68 m are an example of thecommunicating parts. The supply passages 69 y 1, 69 y 2, 69 c 1, 69 c 2,69 m 1, and 69 m 2 are an example of the branched passages. Further,each of the supply ports 49 y 1, 49 y 2, 49 c 1, 49 c 2, 49 m 1, and 49m 2 of color inks is an example of the second supply port and each inkchamber 61 y, 61 c, and 61 m of color inks is an example of the secondliquid chamber.

As illustrated in FIG. 6, when viewed in the up and down directions, thestructure of the passages in the distribution member 32 respectivelysupplying the ink to the two ink supply ports 49 through which the inkof the same color is supplied is of left-right symmetry. That is, thecommunicating hole 68 m of magenta ink is arranged on a straight line L2perpendicular to a line segment L1 joining the two ink supply ports 49 m1 and 49 m 2 (the ink discharge ports 66 m 1 and 66 m 2) of magenta ink.Then, the two supply passages 69 m 1 and 69 m 2 of magenta ink are inline symmetry with respect to the straight line L2. The passages ofyellow ink and of cyan ink also have a passage structure of linesymmetry similar to that of magenta ink. According to thisconfiguration, the difference in the passage resistance between the twosupply passages 69 for the ink of the same color is reduced and hencethe difference in the passage resistance between the two passagesrespectively from one ink chamber 61 to two supply ports 49 is reduced.

In the ink supply section 21 described above, the ink sent from the inkcartridge 30 through the tube 22 to the sub tank 31, first, flows intothe ink chamber 61 corresponding to the ink. Then, the ink having flowedinto the ink chamber 61 is supplied through the connection passage 67 inthe distribution member 32 to the supply port 49 of the head section 20.Here, when air is mixed in the ink supplied through the tube 22 and thenthe air flows into the head section 20, this could cause ejectionfailure in the nozzles 47. In this point, in the present embodiment, theink chamber 61 is present in the upstream of the head section 20. Thus,at the time that the ink flows from the ink chamber 61 to the connectionpassage 67 of the distribution member 32 in the downstream, the airmixed in the ink is separated from the ink and then left in the upperportion of the ink chamber 61. Accordingly, the ink from which air hasbeen separated and removed is supplied from the ink chamber 61 throughthe connection passage 67 of the distribution member 32 to the headsection 20. Here, the air once separated from the ink is collected inthe upper portion of the ink chamber 61. Thus, the air in the inkchamber 61 does not flow into the head section 20 even when the ink islater supplied to the ink chamber 61.

Nevertheless, in association with the consumption of the ink in the headsection 20, the air separated from the ink is continuously collected inthe ink chamber 61 and hence the air collected in the upper portion ofthe ink chamber 61 continues to increase. Then, when the ink chamber 61is filled up with the air, a part of the air flows through theconnection passage 67 to the head section 20. Thus, at each time that afixed time has elapsed, the above-mentioned air discharging purge isperformed so that the air collected in the ink chamber 61 is dischargedthrough the air discharge port 24 a of the air discharge section 24 viathe air discharge passage 65.

As described above, in the present embodiment, the four ink chambers 61of the sub tank 31 are aligned in the conveying direction intersectingwith (perpendicular to) the up and down directions and with the scanningdirection which is the direction of arrangement of the seven supplyports 49. By virtue of this, without the necessity of size increase inthe scanning direction in the sub tank 31, the length of each inkchamber 61 in the scanning direction is allowed to be increased andhence a larger area of each ink chamber 61 is ensured.

Further, in the present embodiment, the ink chambers 61 of the colorinks of three colors have a configuration that an ink of the same colorfrom one ink chamber 61 elongated in the scanning direction is suppliedand distributed to the two supply ports 49 of the head section 20. Inthis point, like in the conventional art, an alternative configurationmay be employed that two ink chambers are aligned in the scanningdirection correspondingly respectively to the two supply ports throughwhich the ink of the same color is supplied. Here, an advantage of theconfiguration of the present embodiment over the alternativeconfiguration is described below. FIG. 7 is a top view of the inkejection device 104 constructed such that the ink chambers 161 in thesame number as the supply ports 149 are aligned in the scanningdirection. In FIG. 7, the sub tank 131 includes seven ink chambers 161respectively corresponding to the seven supply ports 149 of the headsection 20. Then, the seven ink chambers 161 are aligned in the scanningdirection.

In the configuration illustrated in FIG. 7, first, the seven inkchambers 161 are aligned in the scanning direction. Thus, the width ofeach ink chamber 161 in the scanning direction is rather narrow andhence the area is also small. In addition to this problem, the followingproblem also arises. That is, in order that a satisfactory air dischargeproperty should be achieved for the air collected respectively in twoink chambers 161 (e.g., the ink chambers 161 y 1 and 161 y 2 of yellowink) containing an ink of the same color, it is desired that the two inkchambers 161 are linked to each other such that a continuous air flowoccurs from the upstream of the two ink chambers 161, sequentiallythrough the two ink chambers 161 through the air discharge passage 165to the air discharge section 124. Nevertheless, since the ink chamber161 of black ink is present between the two ink chambers 161, the linkpassage 170 linking the two ink chambers 161 of the ink of the samecolor need be arranged on the outer side of these ink chambers 161 suchas to avoid the seven ink chambers 161. For example, in FIG. 7, the linkpassages 170 y, 170 c, and 170 m are arranged on the upstream side ofthe conveying direction relative to the seven ink chambers 161. Thisarrangement of the link passages 170 causes a size increase in the subtank 31 in plan view.

In this point, in the present embodiment, as illustrated in FIG. 2, oneink chamber 61 is provided for each ink of any color and then the fourink chambers 61 are aligned in the conveying direction. By virtue ofthis, the length of each ink chamber 61 in the scanning direction isallowed to be increased and then the ink of the same color is allowed tobe supplied from one ink chamber 61 respectively to the two supply ports49 aligned in the scanning direction. That is, in this configuration,the ink chamber 61 is shared by the two supply ports 49 for the ink ofthe same color. This avoids the necessity of the link passages 170 inFIG. 7 and hence the passage structure is simplified. Further, asindicated by an arrow in FIG. 2, the ink passage of each color in thesub tank 31 becomes a single passage extending from the ink introductionpassage 64 through the ink chamber 61 to the air discharge passage 65without branching in the middle. Thus, the air continuously flows withease and hence the air discharge property in the sub tank 31 isimproved.

Further, as illustrated in FIG. 2, the lengths of the four ink chambers61 in the scanning direction are shorter as the ink chambers 61 arelocated on the more forward side (on a side closer to the inkintroduction passages 64). Then, the ink chambers 61 located on the moreforward side and the ink introduction passages 64 connected to the inkchambers 61 located on the more backward side are aligned in thescanning direction. By virtue of this, the four ink chambers 61 and thefour ink introduction passages 64 supplying the inks respectively to thefour ink chambers 61 are allowed to be arranged compact.

Further, in the present embodiment, as illustrated in FIG. 3, the damperfilm 34 is provided as an upper wall of the sub tank 31 (a part of thewall) forming the ink chambers 61. Thus, each ink chamber 61 serves alsoas a damper chamber attenuating a pressure fluctuation in the ink. Inorder to improve the effect of attenuating the pressure fluctuation inthe damper chamber, it is preferable to increase the area of the damperchamber as large as practical. In this point, as described above, whenthe configuration is employed that the four ink chambers 61 are alignedin the conveying direction, a larger area of each ink chamber 61 servingas the damper chamber is ensured. Further, the ink chamber 61 separatingair from the ink serves also as a damper chamber, thereby further sizereduction is allowed in the ink supply section 21 in comparison with aconfiguration that a damper chamber is provided independently. Further,like in FIG. 7, in the configuration that the seven ink chambers 161 arealigned in the scanning direction, when the area of each ink chamber 161is increased in order that each ink chamber 161 should serve also as adamper chamber, this causes a remarkable size increase in the sub tank131 in the scanning direction. In this point, in the present embodiment,since the four ink chambers 61 are aligned in the conveying direction,the size increase in the sub tank 31 in the scanning direction isallowed to be controlled even in a state that the area of each inkchamber 61 is increased and hence the function of a damper chamber isachieved.

Next, modifications obtained by adding various changes to theabove-mentioned embodiment are described below. Here, like components tothose in the above-mentioned embodiment are designated by like numeralsand hence their description is omitted appropriately.

(Modification 1)

Although in the above-mentioned embodiment, the supply ports 49 of thepassage unit 40 and the ink discharge ports 66 of the distributionmember 32 are arranged in the end part thereof in the upstream (backwardside) of the conveying direction, in Modification 1 the supply ports 49and the ink discharge ports 66 are arranged in the both end partsthereof in the conveying direction. In such a configuration, thedistribution member 32 is constructed so as to be provided with aplurality of layers.

FIG. 8 is a top view of a head section according to Modification 1, andFIGS. 9A to 9D are horizontal sectional views of a distribution member32 according to Modification 1.

As illustrated in FIG. 8, seven supply ports 49 through which magentaink, cyan ink, yellow ink and black ink flow are aligned in the scanningdirection in the end part of the passage unit 40 in the upstream of theconveying direction. The seven supply ports 49 consist of a supply port49 ka of black ink, two supply ports 49 y 1 a and 49 y 2 a of yellowink, two supply ports 49 c 1 a and 49 c 2 a of cyan ink, and two supplyports 49 m 1 a and 49 m 2 a of magenta ink. Also, seven supply ports 49through which magenta ink, cyan ink, yellow ink and black ink flow arealigned in the scanning direction in the end part of the passage unit 40in the downstream of the conveying direction. The seven supply ports 49consist of a supply port 49 kb of black ink, two supply ports 49 y 1 band 49 y 2 b of yellow ink, two supply ports 49 c 1 b and 49 c 2 b ofcyan ink, and two supply ports 49 m 1 b and 49 m 2 b of magenta ink. Theorder in which these supply ports are arranged is similar to that in theabove-mentioned embodiment, and the supply ports 49 ka and 49 kb ofblack ink are arranged in the center portion in the scanning direction.The supply ports 49 y 1 a, 49 y 2 a, 49 y 1 b, 49 y 2 b of yellow ink,the supply ports 49 c 1 a, 49 c 2 a, 49 c 1 b, 49 c 2 b of cyan ink, andthe supply ports 49 m 1 a, 49 m 2 a, 49 m 1 b, 49 m 2 b of magenta inkare arranged in left-right symmetry in the order of the supply ports ofyellow ink, the supply ports of cyan ink, and the supply ports ofmagenta ink starting at the vicinity of the supply ports 49 ka and 49 kbof black ink toward each of the outer sides (both left and right sides)in the scanning direction. In such a configuration, the supply ports 49arranged in the both end parts in the conveying direction are formed inthe both end parts of the manifolds 50.

As illustrated in FIGS. 9A to 9D, the distribution member 32 is providedas the plurality of layers with four plates 32 m, 32 c, 32 y, 32 k andthree films (not illustrated) which are arranged between two plates ofthe four plates, respectively. Communicating hole(s) and ink dischargeports are formed in the four plates 32 m, 32 c, 32 y, 32 k and threefilms, respectively. After the four plates 32 m, 32 c, 32 y, 32 k andthree films are stacked, the communicating holes are communicated witheach other for each color and the ink discharge ports are communicatedwith each other for each color, so as to constitute passages throughwhich inks flow.

As illustrated in FIG. 9A, the plate arranged as the lowermost layeramong the four plates is a plate 32 m, and seven ink discharge ports 66through which magenta ink, cyan ink, yellow ink and black ink flow arealigned in the scanning direction in the end part of the plate 32 marranged as the lowermost layer in the upstream of the conveyingdirection. The seven ink discharge ports 66 consist of an ink dischargeport 66 kma of black ink, two ink discharge ports 66 y 1 ma and 66 y 2ma of yellow ink, two ink discharge ports 66 c 1 ma and 66 c 2 ma ofcyan ink, and two ink discharge ports 66 m 1 ma and 66 m 2 ma of magentaink. Also, seven ink discharge ports 66 through which magenta ink, cyanink, yellow ink and black ink flow are aligned in the scanning directionin the end part of the plate 32 m in the downstream of the conveyingdirection. The seven ink discharge ports 66 consist of an ink dischargeport 66 kmb of black ink, two ink discharge ports 66 y 1 mb and 66 y 2mb of yellow ink, two ink discharge ports 66 c 1 mb and 66 c 2 mb ofcyan ink, and two ink discharge ports 66 m 1 mb and 66 m 2 mb of magentaink. The ink discharge ports are arranged in left-right symmetry in theorder of yellow, cyan and magenta while the ink discharge ports of blackink are centrally arranged.

In the plate 32 m, a H-shaped connection passage 67 m is formed that isa passage for magenta ink. The H-shaped connection passage 67 m is ofleft-right symmetry with respect to a line segment L2 joining the twoink discharge ports 66 kma and 66 kmb of black ink. The connectionpassage 67 m includes a communicating hole 68 mm in communication withthe ejection hole 62 m of the sub tank 31 and a supply passage 69 mconnecting the communicating hole 68 mm to the four ink discharge ports66 m 1 ma, 66 m 2 ma, 66 m 1 mb, 66 m 2 mb. The communicating hole 68 mmis arranged on the line segment L2 in the center portion in the scanningdirection. The supply passage 69 m is constructed such that two supplypassages extend from the communicating hole 68 mm on the left or rightside and branch into two passages, respectively, to be connected to theink discharge ports 66 m 1 ma, 66 m 2 ma, 66 m 1 mb, 66 m 2 mb.

As illustrated in FIG. 9B, the plate arranged as the second layer fromthe bottom among the four plates is a plate 32 c, and five ink dischargeports 66 through which cyan ink, yellow ink and black ink flow arealigned in the scanning direction in the end part of the plate 32 c inthe upstream of the conveying direction. The five ink discharge ports 66consist of an ink discharge port 66 kca of black ink, two ink dischargeports 66 y 1 ca and 66 y 2 ca of yellow ink, and two ink discharge ports66 c 1 ca and 66 c 2 ca of cyan ink. Also, five ink to discharge ports66 through which cyan ink, yellow ink and black ink flow are aligned inthe scanning direction in the end part of the plate 32 c in thedownstream of the conveying direction. The five ink discharge ports 66consist of an ink discharge port 66 kcb of black ink, two ink dischargeports 66 y 1 cb and 66 y 2 cb of yellow ink, and two ink discharge ports66 c 1 cb and 66 c 2 cb of cyan ink. The ink discharge ports arearranged in left-right symmetry in the order of yellow and cyan whilethe ink discharge ports of black ink are centrally arranged.

In the plate 32 c, a H-shaped connection passage 67 c is formed that isa passage for cyan ink. The H-shaped connection passage 67 c is ofleft-right symmetry with respect to a line segment L2 joining the twoink discharge ports 66 kca and 66 kcb of black ink. The connectionpassage 67 c includes a communicating hole 68 cc in communication withthe ejection hole 62 c of the sub tank 31 and a supply passage 69 cconnecting the communicating hole 68 cc to the four ink discharge ports66 c 1 ca, 66 c 2 ca, 66 c 1 cb, 66 c 2 cb. The communicating hole 68 ccis arranged on the line segment L2 in the center portion in the scanningdirection. The supply passage 69 c is constructed such that two supplypassages extend from the communicating hole 68 cc on the left or rightside and branch into two passages, respectively, to be connected to theink discharge ports 66 c 1 ca, 66 c 2 ca, 66 c 1 cb, 66 c 2 cb.Moreover, in the plate 32 c, a communiting hole 68 mc through whichmagenta ink flows is formed on the line segment L2 in the center portionin the scanning direction, in addition to the communicating hole 68 cc.

As illustrated in FIG. 9C, the plate arranged as the third layer fromthe bottom among the four plates is a plate 32 y, and three inkdischarge ports 66 through which yellow ink and black ink flow arealigned in the scanning direction in the end part of the plate 32 y inthe upstream of the conveying direction. The three ink discharge ports66 consist of an ink discharge port 66 kya of black ink and two inkdischarge ports 66 y 1 ya and 66 y 2 ya of yellow ink. Also, three inkdischarge ports 66 through which yellow ink and black ink flow arealigned in the scanning direction in the end part of the plate 32 y inthe downstream of the conveying direction. The three ink discharge ports66 consist of an ink discharge port 66 kyb of black ink and two inkdischarge ports 66 y 1 yb and 66 y 2 yb of yellow ink. The ink dischargeports of yellow ink are arranged in left-right symmetry on both sides ofthe ink discharge ports of black ink while the ink discharge ports ofblack ink are centrally arranged.

In the plate 32 y, a H-shaped connection passage 67 y is formed that isa passage for yellow ink. The H-shaped connection passage 67 y is ofleft-right symmetry with respect to a line segment L2 joining the twoink discharge ports 66 kya and 66 kyb of black ink. The connectionpassage 67 y includes a communicating hole 68 yy in communication withthe ejection hole 62 y of the sub tank 31 and a supply passage 69 yconnecting the communicating hole 68 yy to the four ink discharge ports66 y 1 ya, 66 y 2 ya, 66 y 1 yb, 66 y 2 yb. The communicating hole 68 yyis arranged on the line segment L2 in the center portion in the scanningdirection. The supply passage 69 y is constructed such that two supplypassages extend from the communicating hole 68 yy on the left or rightside and branch into two passages, respectively, to be connected to theink discharge ports 66 y 1 ya, 66 y 2 ya, 66 y 1 yb, 66 y 2 yb.Moreover, in the plate 32 y, a communicating hole 68 my through whichmagenta ink flows and a communicating hole 68 cy through which cyan inkflows are formed on the line segment L2 in the center portion in thescanning direction, in addition to the communicating hole 68 yy.

As illustrated in FIG. 9D, the plate arranged as the uppermost layeramong the four plates is a plate 32 k, and an ink discharge port 66 kkathrough which black ink flows is arranged in the end part of the plate32 k in the upstream of the conveying direction, and an ink dischargeport 66 kkb through which black ink flows is arranged in the end part ofthe plate 32 k in the downstream of the conveying direction. In theplate 32 k, a connection passage 67 k is formed that is a passage forblack ink. The connection passage 67 k includes a communicating hole 68kk in communication with the ejection hole 62 k of the sub tank 31 and asupply passage 69 k connecting the communicating hole 68 kk to the twoink discharge ports 66 kka and 66 kkb. The communicating hole 68 kk isarranged on a line segment L2 joining the two ink discharge ports 66 kkaand 66 kkb of black ink in the center portion in the scanning direction.The supply passage 69 k includes a supply passage extending from thecommunicating hole 68 kk to the ink discharge port 66 kka and a supplypassage extending from the communicating hole 68 kk to the ink dischargeport 66 kkb. Moreover, in the plate 32 k, a communicating hole 68 mkthrough which magenta ink flows, a communicating hole 68 ck throughwhich cyan ink flows and a communicating hole 68 yk through which yellowink flows are formed on the line segment L2 in the center portion in thescanning direction, in addition to the communicating hole 68 kk. Thesupply passage extending from the communicating hole 68 kk to the inkdischarge port 66 kkb is bent so as to avoid these communicating holes.

After the four plates 32 m, 32 c, 32 y, 32 k constructed in the abovemanner and the three films (not illustrated) which are arranged betweentwo plates of the four plates, respectively are stacked, the inkdischarge ports 66 formed in the respective plates are communicated witheach other for each color and the communicating holes 68 formed in therespective plates are communicated with each other for each color, so asto constitute passages through which inks flow. Moreover, the total of14 ink discharge ports 66 formed in the both end parts in the conveyingdirection are respectively connected through the communicating members36 to the total of 14 ink supply ports 49 of the head section 20.

In Modification 1, for such a configuration, the connection passages arenot bent up and down, and the connection passages of inks of therespective colors intersect with each other when seen up and down,thereby bent portions of the connection passages are reduced that an inkflow is easy to collect. Here, the shape of the connection passageformed in the each plate is not limited to the above-mentionedconfiguration. For example, although in the above-mentionedconfiguration the two supply passages extend from the communicating holeon the left or right side and branch into two passages, respectively, tobe connected to the ink discharge ports, for magenta ink, cyan ink andyellow ink, four supply passages may extend from a communicating hole,respectively to be connected to ink discharge ports. Also, although inthe above-mentioned configuration the supply passages are constructed tobe linear, the configuration of the supply passage is not limited to belinear and may be constructed to contain a curve. Moreover, the order inwhich the four plates are stacked is not limited to the above-mentionedorder. In addition, although in the above-mentioned configuration thefilm is arranged between the plate and the plate, employableconfigurations are not limited to this arrangement. Instead of the film,another plate may be arranged between the plate and the plate.Furthermore, the supply ports and the ink discharge ports may not bearranged in left-right symmetry in the order of black, yellow, cyan andmagenta. For example, on both of the right and left sides of the supplyports and the ink discharge ports of black ink, the supply ports and theink discharge ports of the color inks of three colors may be arranged inthe same order of magenta→cyan→yellow from left to right, and the orderof colors may be any order.

In the printer 1, when a negative pressure in a passage due to a waterhead difference between a meniscus formed in an opening of the nozzle 47and a liquid surface of ink stored in the ink chamber 61 falls below ameniscus withstanding pressure not for breaking a meniscus formed in thenozzle 47, the meniscus is broken, air intrudes into the passage, andthen a state of inability to eject may be caused. Specifically,immediately after ejection of ink, a pressure in a passage becomessuddenly large toward a side of the negative pressure. Therefore, thedamper film 34 is provided as a wall of the ink chamber so that thenegative pressure in the passage does not fall below the meniscuswithstanding pressure, thereby a negative pressure fluctuation isabsorbed by a deformation of the damper film 34.

In Modification 1, the supply ports 49 are provided in the both endparts in the conveying direction, therefore, a distance between thesupply port 49 and the nozzle 47 furthermost from the supply port 49 issmall, as compared with the configuration where the supply ports 49 areprovided in only one end part in the conveying direction. In a casewhere the distance is small, the passage resistance between the inkchamber 61 and the nozzle 47 is small, and a pressure loss of thepassage is also small. Accordingly, since the pressure loss is small inModification 1 as compared with the configuration where the supply portsare provided in only one end part, a negative pressure in a passageimmediately after ejection of ink is small.

Consequently, since a negative pressure in a passage immediately afterejection of ink is small in Modification 1, the negative pressure in thepassage does not fall below the meniscus withstanding pressure even whena negative pressure to be absorbed by the damper film 34 is small. Sincea performance of the damper film 34 is proportional to an area of thedamper film 34, a size of the damper film 34 can be reduced.

(Modification 2)

Although in the above-mentioned embodiment, the supply ports 49 of thepassage unit 40 and the ink discharge ports 66 of the distributionmember 32 are arranged in the end part thereof in the upstream (backwardside) of the conveying direction, in Modification 2 the supply ports 49and the ink discharge ports 66 are arranged in a region other than theboth end parts thereof in the conveying direction.

FIG. 10 is a top view of a head section according to Modification 2, andFIG. 11 is horizontal sectional views of a distribution member 32according to Modification 2.

As illustrated in FIG. 10, seven supply ports 49 through which magentaink, cyan ink, yellow ink and black ink flow are aligned in the scanningdirection in a region of a middle part other than the both end parts ofthe passage unit 40 in the conveying direction. The seven supply ports49 consist of a supply port 49 k of black ink, two supply ports 49 y 1and 49 y 2 of yellow ink, two supply ports 49 c 1 and 49 c 2 of cyanink, and two supply ports 49 m 1 and 49 m 2 of magenta ink. The supplyports are arranged in left-right symmetry in the order of the supplyport 49 y 1 and 49 y 2 of yellow ink, the supply port 49 c 1 and 49 c 2of cyan ink, and the supply port 49 m 1 and 49 m 2 of magenta ink whilethe supply port 49 k of black ink is centrally arranged. In such aconfiguration, the supply ports 49 arranged in a region of the middlepart other than the both end parts of the passage unit 40 in theconveying direction are formed in a region of a middle part other thanthe both end parts of the manifolds 50. Here, although the supply portsare arranged in left-right symmetry in the order of the supply port 49 kof black ink, the supply ports 49 y 1 and 49 y 2 of yellow ink, thesupply ports 49 c 1 and 49 c 2 of cyan ink, and the supply ports 49 m 1and 49 m 2 of magenta ink, they may not be arranged in this order, andthe order of colors may be any order.

As illustrated in FIG. 11, seven ink discharge ports 66 are formed inthe region of the middle part other than the both end parts of thedistribution member 32 in the conveying direction, are aligned in thescanning direction, and are arranged at positions located immediatelyabove the seven supply ports 49 of the supply unit 40. The seven inkdischarge ports 66 consist of an ink discharge port 66 k of black ink,two ink discharge ports 66 y 1 and 66 y 2 of yellow ink, two inkdischarge ports 66 c 1 and 66 c 2 of cyan ink, and two ink dischargeports 66 m 1 and 66 m 2 of magenta ink. The ink discharge ports arearranged in left-right symmetry in the order of yellow, cyan and magentawhile the ink discharge port of black ink is centrally arranged. Also,the seven ink discharge ports 66 are respectively connected through thecommunicating members 36 to the seven ink supply ports 49 of the headsection 20. Here, although the ink discharge ports are arranged inleft-right symmetry in the order of black, yellow, cyan and magenta,they may not be arranged in this order, and the order of colors may beany order.

Moreover, the distribution member 32 is provided with four connectionpassages 67 respectively for supplying inks of four colors sent throughthe ejection holes 62 from the four ink chambers 61 of the sub tank 31,to the seven supply ports 49 of the head section 20. Each of the threeconnection passages 67 of magenta ink, cyan ink and yellow ink includesa communicating hole 68 in communication with the ejection hole 62 ofthe sub tank 31 and a supply passage 69 connecting the communicatinghole 68 to the ink discharge ports 66, and is arranged in left-rightsymmetry with respect to a straight line L2 perpendicular to a linesegment L1 joining the two ink discharge ports 66 m 1 and 66 m 2 ofmagenta ink. On the other hand, in the connection passage 67 of blackink, a communicating hole 68 k and an ink discharge port 66 k overlapwith each other in the up and down directions, thus the connectionpassage 67 does not include a supply passage. The four communicatingholes 68 are different from those in the above-mentioned embodiment, andare arranged on the straight line L2 in the center portion of thedistribution member 32 in the scanning direction in the order ofmagenta, black, yellow and cyan from the backward to the forward.According to the arrangement of the communicating holes, the four inkchambers 61 and the four ejection holes 62 of the sub tank 31 arearranged in the forward and backward directions in correspondence to thearrangement of the communicating holes 68.

In Modification 2, the supply passage 69 m of magenta ink of thedistribution member 32 extends from the communicating hole 68 m on theleft or right side, is bent in the middle so as to extend forward andthen is connected to the ink discharge ports 66 m 1 and 66 m 2. Thesupply passage 69 c of cyan ink and the supply passage 69 y of yellowink respectively extend from the communicating hole 68 c and thecommunicating hole 68 y on the left or right side, are bent in themiddle so as to extend backward and then are connected to the inkdischarge ports 66 c 1 and 66 c 2 and the ink discharge ports 66 y 1 and66 y 2.

In the above-mentioned embodiment, the pressure chambers 51 and thepiezoelectric actuator 41 are arranged above the manifold 50, and in acase where the configuration in which “the supply ports are arranged inthe region other than the both end parts in the conveying direction” isapplied to such a configuration, the pressure chambers 51 and thepiezoelectric actuator 41 are required to be arranged around the supplyports. However, in a case where as illustrated in FIG. 12, the manifold50 is arranged between the ink supply section 21 and the individualpassage containing the pressure chamber 51 and the nozzle 47 in the upand down directions, the above-mentioned problem does not occur.

Here, in Modification 2, the manifold 50 is arranged between the inksupply section 21 and the individual passage containing the pressurechamber 51 and the nozzle 47, but the arrangement of the manifold is notlimited to this. For example, the manifold may be aligned with thepressure chamber and the nozzle on the left or right side.

According to Modification 2, a distance between the supply port and thenozzle furthermost from the supply port is small, as compared with theconfiguration where the supply ports are provided in only one end part.Thus, Modification 2 brings about the similar effect as that inModification 1. Furthermore, in Modification 2, the configuration of theconnection passage is simpler than that in Modification 1 to furtherprevent the pressure loss.

In the above-mentioned embodiment, the lengths of the four ink chambers61 in the scanning direction are different from each other and hence theareas of the four ink chambers 61 are also different from each other.Thus, it is preferable that the ink chamber 61 located on the mostbackward side (the side opposite to the ink supply side) and having thegreatest length in the scanning direction (also the greatest area)contains an ink whose collected air increases most rapidly.

For example, an ink having the highest ink consumption rate in the headsection 20 may be supplied to the ink chamber 61 located on the mostbackward side. For example, black ink used in both of text printing andcolor printing and hence tending to have the highest ink consumptionrate may be supplied to the ink chamber 61 located on the most backwardside. Further, in the head section 20, in a case that the number ofnozzles 47 ejecting a given ink (e.g., black ink) is greater than thenumber of nozzles 47 ejecting the inks of other kinds, the consumptionrate of the given ink tends to be high. Thus, in this case, the givenink is supplied to the ink chamber 61 located on the most backward side.

Further, in some cases, the easiness of air mixing is different amongthe inks of four colors because of a difference in the thickness, thematerial, or the like among the four tubes 22 respectively supplying theinks of four colors. In this case, an ink having the highest air mixingeasiness may be supplied to the ink chamber 61 located on the mostbackward side and an ink having the lowest air mixing easiness may besupplied to the ink chamber 61 located on the most forward side.

As illustrated in FIG. 13, the lengths of the four ink chambers 61 inthe scanning direction may be equal to each other. In this case, theareas of all four ink chambers 61 are allowed to be increased.Nevertheless, as illustrated in FIG. 13, in a case that the ink is to besupplied to the sub tank 31 from the forward side, the ink introductionpassage 64 supplying the ink to the ink chamber 61 located on thebackward side need be arranged on the left side such as to bypass theink chambers 61 on the forward side. This causes a disadvantage of sizeincrease in the sub tank 31 in the scanning direction.

Here, as illustrated in FIG. 14, a tube joint 23 may be provided on theleft side-surface of the portion of the sub tank 31 where the four inkchambers 61 are formed. In this case, the four ink introduction passages64 are formed such as to extend in the scanning direction in order thatthe tube joint 23 on the left side should be linearly joinedrespectively to the four ink chambers 61 on the right side. In FIG. 14,in contrast to FIG. 13, the necessity is avoided that the size of thesub tank 31 should be increased in the scanning direction in order toensure an arrangement region for the four ink introduction passages 64.Further, the necessity is avoided that a region necessary forarrangement of the tube joint 23 should be ensured in the forward endpart of the sub tank 31. This permits size reduction of the sub tank 31also in the conveying direction.

In the above-mentioned embodiment, the connection passages 67 in thedistribution member 32 have a passage structure of left-right symmetry(line symmetry). However, such a line symmetric structure is notindispensable. For example, even when two right and left supply passages(branched passages) through which an ink of the same color flows havemutually different lengths, the difference in the passage resistance ofthe two supply passages is allowed to be reduced by employing mutuallydifferent passage widths.

Further, employable configurations are not limited to that oneconnection passage 67 connected to the ink chamber 61 is branched in themiddle. That is, a configuration may be employed that two connectionpassages 67 are respectively connected to one ink chamber 61 and thenthe ink is independently supplied through the two connection passages 67to the two supply ports 49.

In the above-mentioned embodiment, in the head section 20, two supplyports 49 are provided for each of the color inks of three colorsconsisting of yellow, cyan, and magenta and then the supply ports 49 ofthese color inks are arranged separately onto each of the right and leftsides of the supply port 49 k of black ink. In contrast, as illustratedin FIG. 15, the head section 20 may have a configuration that one supplyport 49 alone is provided for each ink of any color. Here, in this case,in contrast to the above-mentioned embodiment, in the distributionmember 32 between the sub tank 31 and the head section 20, theconnection passage 67 connected to one ink chamber 61 need not bedivided into two in order to supply the ink respectively to the twosupply ports 49.

In the above-mentioned embodiment, the flexible damper film 34 isprovided as the upper wall of the sub tank 31 (a part of the wall)forming the ink chambers 61 and then the ink chambers 61 serve as damperchambers. However, this configuration is not indispensable. That is,damper chambers provided with the damper film 34 may be providedseparately from the ink chambers 61. Further, in a case that thepressure fluctuation generated in the passages in the sub tank 31 isrelatively small, the damper film 34 may be omitted.

As described above, the above-mentioned embodiment and the modificationsthereof are applied to an ink ejection device of an ink jet printerejecting ink onto recording paper so as to print an image or the like.In addition, the embodiment and the modifications may be applied also toa liquid ejection device used in various applications other thanprinting of an image or the like. For example, the embodiment and themodifications may be applied also to a liquid ejection device ejectingan electrically conductive liquid onto a substrate so as to form anelectrically conductive pattern on a surface of the substrate.

As this description may be embodied in several forms without departingfrom the spirit of essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive, since thescope is defined by the appended claims rather than by the descriptionpreceding them, and all changes that fall within metes and bounds of theclaims, or equivalence of such metes and bounds thereof are thereforeintended to be embraced by the claims.

What is claimed is:
 1. A liquid ejection device comprising: a liquidsupply section including a plurality of liquid chambers respectivelyconfigured to contain plural kinds of liquids; and a liquid ejectionsection including plural nozzle groups of one or plural nozzle(s) andconfigured to eject the plural kinds of liquids to be supplied from theliquid supply section, wherein the liquid ejection section includes aplurality of supply ports which are aligned in a first direction andthrough which the plural kinds of liquids are supplied, wherein theliquid supply section includes: a plurality of connection passagesrespectively connecting the plurality of supply ports of the liquidejection section to the liquid chambers configured to contain theliquids to be supplied respectively to the supply ports; and a pluralityof air discharge passages connected respectively to the plurality ofliquid chambers, and wherein the plurality of liquid chambers arealigned in a second direction intersecting with the first direction. 2.The liquid ejection device according to claim 1, wherein the supplyports include one or plural first supply port(s) through which a firstliquid among the plural kinds of liquids is supplied and plural secondsupply ports through which a second liquid among the plural kinds ofliquids is supplied, the liquid chambers include a first liquid chamberconfigured to contain the first liquid and a second liquid chamberconfigured to contain the second liquid, and the connection passagesinclude a first connection passage connecting the first liquid chamberto the one or plural first supply port(s) and a second connectionpassage connecting the plural second supply ports to the second liquidchamber.
 3. The liquid ejection device according to claim 2, wherein thesupply ports include one first supply port and two second supply ports,and the two second supply ports are arranged on both sides of the onefirst supply port.
 4. The liquid ejection device according to claim 3,wherein the second connection passage includes a communicating partcommunicating with the second liquid chamber and two branched passagesconnecting the communicating part to the two second supply ports, thecommunicating part is arranged on a straight line that is perpendicularto a line segment joining the two second supply ports and that passesthrough a middle point of the line segment, and the two branchedpassages are in line symmetry with respect to the straight line.
 5. Theliquid ejection device according to claim 1, wherein the plurality ofsupply ports are arranged in one end part of the liquid ejection sectionin the second direction.
 6. The liquid ejection device according toclaim 5, wherein the liquid ejection section further includes aplurality of common passages respectively through which the liquids aresupplied from the plurality of supply ports and a plurality ofindividual passages respectively which branch from the common passagesand extend to the nozzles, and the plurality of supply ports are formedin end parts of the plurality of common passages, respectively.
 7. Theliquid ejection device according to claim 1, wherein the plurality ofsupply ports are arranged in a region other than both end parts of theliquid ejection section in the second direction.
 8. The liquid ejectiondevice according to claim 7, wherein the liquid ejection section furtherincludes a plurality of common passages respectively through which theliquids are supplied from the plurality of supply ports and a pluralityof individual passages respectively which branch from the commonpassages and extend to the nozzles, and the plurality of supply portsare formed in the plurality of common passages, respectively, and adistance between each supply port and one end of each common passage isequal to a distance between each supply port and the other end of eachcommon passage.
 9. The liquid ejection device according to claim 7,wherein the liquid ejection section further includes a plurality ofcommon passages respectively through which the liquids are supplied fromthe plurality of supply ports and a plurality of individual passagesrespectively which branch from the common passages and extend to thenozzles, and the liquid ejection section is arranged on one side of theliquid supply section in a third direction intersecting with the firstdirection and the second direction, and the plurality of common passagesare arranged between the liquid supply section and the individualpassages in the third direction.
 10. The liquid ejection deviceaccording to claim 2, wherein the supply ports include two pairs of onefirst supply port and two second supply ports, and the two second supplyports are arranged on both sides of the one first supply port for eachpair.
 11. The liquid ejection device according to claim 10, wherein thesecond connection passage includes a communicating part communicatingwith the second liquid chamber and four branched passages connecting thecommunicating part to the four second supply ports, the communicatingpart is arranged on a straight line joining the two first supply ports,and the four branched passages are in line symmetry with respect to thestraight line.
 12. The liquid ejection device according to claim 11,wherein the first connection passage and the second connection passageare arranged at positions different from each other in a third directionintersecting with the first direction and the second direction.
 13. Theliquid ejection device according to claim 10, wherein the two pairs offirst and second supply ports are arranged in both end parts of theliquid ejection section in the second direction.
 14. The liquid ejectiondevice according to claim 10, wherein the liquid ejection sectionincludes a plurality of common passages respectively through which theliquids are supplied from the plurality of supply ports and a pluralityof individual passages respectively which branch from the commonpassages and extend to the nozzles, and the supply ports are formed inend parts of the plurality of common passages.
 15. The liquid ejectiondevice according to claim 14, wherein the supply ports are formed inboth end parts of the plurality of common passages.
 16. The liquidejection device according to claim 1, wherein a damper film havingflexibility is provided as a part of a wall forming the liquid chambers.17. The liquid ejection device according to claim 1, wherein the liquidsupply section includes a plurality of liquid introduction sectionsrespectively connecting the plurality of liquid chambers to a pluralityof liquid storage sections respectively configured to store the pluralkinds of liquids, the liquid introduction sections being arranged on oneside of the liquid chambers in the first direction.
 18. The liquidejection device according to claim 17, wherein the plurality of liquidchambers are connected to the plurality of air discharge passages on theother side of the liquid chambers in the first direction.
 19. The liquidejection device according to claim 17, wherein lengths of the pluralityof liquid chambers in the first direction are equal to each other. 20.The liquid ejection device according to claim 1, wherein the liquidsupply section includes a plurality of liquid introduction sectionsrespectively connecting the plurality of liquid chambers to a pluralityof liquid storage sections respectively configured to store the pluralkinds of liquids, the liquid introduction sections being arranged on oneside of the liquid chambers in the second direction, and lengths of theplurality of liquid chambers in the first direction are shorter in anorder of arrangement of the liquid chambers toward the one side in thesecond direction.
 21. The liquid ejection device according to claim 20,wherein the number of nozzles of one nozzle group among the pluralnozzle groups of nozzle(s) is larger than the number of nozzle(s) of theother nozzle group, and a liquid to be contained in the liquid chamberhaving the greatest length in the first direction is a liquid to beejected through the nozzles of the one nozzle group.
 22. The liquidejection device according to claim 1, further comprising an airdischarge section connected to the air discharge passages and configuredto discharge air in the liquid chambers.
 23. The liquid ejection deviceaccording to claim 2, wherein the plural nozzle groups include a firstnozzle group through which the first liquid is supplied and pluralsecond nozzle groups through which the second liquid is supplied, andthe plural second nozzle groups are arranged on both sides of the firstnozzle group.